Pierce nuts were invented and commercially developed by the predecessor in interest of the assignee of this application primarily for mass production applications for the automotive and appliance industries. As will be understood by those skilled in this art, a pierce nut includes a projecting pilot portion which punches an opening in a panel and the pierce nut is then installed in the pierced opening by a die member or die button. In a typical application, one die member or die platen, typically the upper die member, includes a pierce nut installation apparatus or head having a reciprocating plunger and the opposed die member includes a die button opposite the plunger of the installation head. A pierce nut is installed in a panel supported on the die button with each stroke of the die press. There are various types of pierce nuts available from the assignee of this application generally including a central projecting pilot portion which pierces or punches an opening in the panel, a bore through the pilot portion which is generally threaded, flange portions on at least opposed sides of the pilot portion and panel receiving grooves located either in the pilot portion or the end face of the flange portion. Pierce nuts may be formed in a rolling process or by cold heading.
A conventional pierce nut installation apparatus or installation head includes a pierce nut feed passage receiving pierce nuts for installation by the installation apparatus, a plunger passage communicating with the feed passage receiving pierce nuts from the plunger passage and a plunger reciprocating through the plunger passage generally having a planar end face which engages a pierce nut received in the plunger passage and drives the pierce nut through the plunger passage against a metal panel located opposite the plunger passage on a die button as described above.
There are two problems associated with the installation of pierce nuts utilizing a conventional pierce nut installation apparatus which is addressed by the pierce nut installation apparatus of this invention. One problem is accurately locating a pierce nut in a panel. As will be understood by those skilled in this art, several pierce nuts may be simultaneously installed in a panel with each stroke of the die press and a second element may be attached to the panel with bolts or the like utilizing more than one pierce nut, requiring very accurate placement of the pierce nuts in the panel. At present, the datums for alignment are measured between the circumference of the thread cylinders of the pierce nuts, requiring several datums for each pierce nut installation. It would be desirable, however, to measure the datums between the axes of the bores of the pierce nuts, significantly reducing the datums, but no method or apparatus has yet been developed which permits measurement of the datums between the axes of the pierce nut bores. As mass production methods become more sophisticated, this has become a more serious problem.
Another problem associated with pierce nut installation apparatus is cocking of the pierce nut in the plunger passage. This problem may be reduced by the use of fingers which receive the pierce nuts and travel with the pierce nuts to the panel during installation of the pierce nuts by the plunger.
The pierce nut installation apparatus of this invention eliminates the problems of accurately locating the pierce nuts installed in a panel, significantly reducing the required number of datums, and substantially eliminates cocking of the pierce nuts in the plunger passage.